Repeat after the mu'adhhin when you hear them calling for prayer .

The hadith narrated by Abu Sa’id Al-Khudri states that when one hears the call to prayer from a mu’adhdhin or muezzin, they should repeat after him what he says. This is an important part of Islamic practice as it helps to remind Muslims that it is time for prayer and encourages them to join in with their fellow worshippers. It also serves as a reminder of Allah's greatness and power and helps Muslims focus on their faith during this time. Additionally, repeating after the mu’adhdhin can help those who are new to Islam learn how to properly recite prayers in Arabic. This hadith teaches us about the importance of following Islamic practices and being mindful of our faith at all times.